1. Field of the Invention
The field of the invention relates to a method for assembling innerspring constructions of pocketed coil springs and an apparatus for practicing the method.
2. Brief Description of the Prior Art
Pocketed coil springs have been employed in the assembly of innerspring constructions for many years. The connection of such coil springs has evolved from early constructions where links and hog rings were used to secure adjacent springs. U.S. Pat. Nos. 698,529 and 2,320,153 disclose such constructions. The utilization of rings is slow and expensive as the operator not only has to position the coils, but also must apply the ring by piercing the pocket wrap material while catching the wire defining the top convolution of the coil spring.
A manufacturing process having greater efficiency than the above was developed wherein a length of connected pocketed coil springs is positioned in a sinuous pattern on a rack. Lengths of twine are pulled through each row of pocketed springs thereby connecting them. The twine is then tied off by the operator. Tightness of the construction is dependent upon operator skill. This method remains in use today and improved equipment has been developed therefor. U.S. Pat. No. 4,393,792 discloses an apparatus which improves the efficiency of the basic method.
More recently, an apparatus has been developed for ultrasonically bonding rows of pocketed coil springs together to form an arrangement as shown in U.S. Pat. No. 4,234,984. U.S. Pat. No. 4,401,501 discloses such an apparatus.